In semiconductor manufacturing process, semiconductor wafers, which serve as fundamental materials, will be contaminated by various factors such as metal impurities. Those contaminants will cause defects in chips made from the wafers, such that the chips may fail electrical tests. As a result, the yield of chips is reduced and thus the cost of manufacturing chips is increased.
Metals tend to generate positive ions due to their active chemical property. Such positive ions may cause various problems such as increase in the leakage current, reduction of the life time of minority carriers, and the like. Furthermore, the metal ions may move across a device for a long time after electrical tests and transportation of the device, which may cause failure of devices.
From this point of view, there is a need for a novel method for manufacturing a semiconductor wafer, by which it is possible to purify the semiconductor wafer, and especially to remove the metal impurities therein.